WASHINGTON — A British customs agent who investigated the nuclear smuggling network of Pakistani scientist Abdul Qadeer Khan has himself become the target of a British criminal probe after being prominently featured in a book by American researchers.

Atif Amin’s house and car were searched last week by British authorities with warrants alleging violations of the country’s Official Secrets Act, according to legal documents obtained by The Washington Post.

The action came less than two months after the publication of “America and the Islamic Bomb,” which chronicles Amin’s efforts to uncover the Khan network in 2000, more than three years before U.S. and British intelligence officials broke up the smuggling ring.

The book’s authors, David Armstrong and Joseph Trento, contend that Western intelligence agencies knowingly allowed the smuggling ring to operate for years before moving to shut it down.

During this interlude, Khan passed nuclear parts and know-how to Iran, North Korea and Libya, the authors contend. U.S. officials familiar with the case have acknowledged that the Bush administration confronted Pakistan about Khan’s activities in 2003.

Allied effort to hide story?

“It’s a story Washington and London do not want out,” said Armstrong, who, with Trento, works for the National Security News Service, a Washington-based nonprofit that hires investigative journalists to research security and intelligence topics.

“If Amin can be discredited, it would distract the public from the fact that the U.S. and Britain prevented the most dangerous nuclear smuggling operation in history from being shut down when the opportunity existed,” Armstrong said.

Amin, who formerly led a counterproliferation unit of the British customs service’s commercial fraud division, could not be reached for comment.

In the book, Amin is described as the director of Operation Akin, a customs investigation that in 2000 began targeting Persian Gulf- based companies allegedly involved in the trafficking of militarily sensitive technology.

While working on the investigation in Dubai, Amin began tracing the flow of nuclear-related equipment through companies with ties to Khan, a Pakistani engineer and a key player in his country’s decades-long effort to build nuclear weapons.

Pulled off case in 2000

In the spring of 2000, as Amin closed in on Khan at the center of the smuggling operation, he was ordered to quit the case and return to Britain, the authors state. The reason given to Amin for the abrupt change was that British and U.S. spies who were monitoring the network were worried that his questioning would disrupt their operation and expose informants.

Amin complied with his orders, but in the book he is depicted as complaining bitterly about what he says was a missed opportunity to crush the smuggling ring early.

“They knew exactly what was going on all the time,” Amin is quoted as saying. “If they’d wanted to, they could have blown the whistle on this long ago.”

Other independent researchers, including Ron Suskind, a journalist and author of “The One Percent Doctrine,” have alleged that Western governments were aware of Khan’s nuclear trading years before President Bush announced the takedown of the ring.

Khan acknowledged his role in a February 2004 speech televised in Pakistan, but he insisted that Pakistan’s military and government leaders had no knowledge of his activities at the time.